A conventional rotary switch, such as “Rotary switch” disclosed in R.O.C. patent publication No. 252616 includes a case housing a spindle which has an upper end forcefully coupled with a shade turnable under an external force. The bottom end of the spindle is coupled with a conductive element in a compact manner at a desired location, and also is screwed on a base tray at the bottom of the case. The base tray has a plurality of pins and a common pin at selected locations to connect jutting portions at two ends of the conductive element. When in use, such for a fan to control rotation speed, the wire of various rotation speeds (slow speed, medium speed, fast speed and the like) are connected to the pins of the base tray. A power supply end is soldered on the common pin. By turning the shade at the upper end of the spindle, the jutting portions at two ends of the conductive element are driven and moved to connect the pins on the base tray and the common pin, therefore the fan can be activated. By turning the spindle to make the conductive element to connect another pin and the common pin, a desired rotation speed can be selected. However, the conventional rotary switch mentioned above still has flaws, such as the gap between the shade and the spindle is too large and the shade is prone to tilt, and turning could be difficult or faulty instructions could be output. Coupling of the shade and the spindle could also deform or damage the shade or the conductive element. After used for a period of time, the shade could be idly turned under the force and fail to drive the spindle, and could result in erroneous instruction output of the rotary switch.
To overcome the aforesaid drawbacks, another rotary switch has been developed that has a base and a rotary disk coupling with the base and movable on a rotation track relative to the base. A housing space is formed between the base and the rotary disk to hold signal elements. The signal elements output corresponding instructions according to the rotary disk moving on the rotation track. The rotary switch is coupled with a shade which has a latch portion engageable with a latch trough formed on the rotary disk. The shade can be turned under force so such that the latch portion and the latch trough drive the rotary switch to move on the rotation track. By means of such an approach the rotary disk is moved when the shade receives the external force along the rotation track to generate signals. As the rotary disk and the shade are coupled through the latch means, they do easily loosen off or tilted. Thus a firmer coupling between the rotary switch and the shade can be accomplished to generate more accurate instructions.
However, the rotary switches previously discussed cannot be clearly seen and easily turned to the correct position in a dark or poorly lit environment. Faulty operation tends to occur. Hence how to improve the problems mentioned above still is an issue pending to be resolved in the industry.